Method and apparatus for reforming fuel

ABSTRACT

A gas mixture containing a fuel, water and air is supplied to one end of a reforming room, and a reformed gas containing hydrogen is discharged from the other end thereof. Two or more such reforming units are connected in series, and the upstream part of each reforming room is filled with a first catalyst which catalyzes a partial oxidation reaction in an oxygen-rich environment, and the downstream part is filled with a second catalyst which performs the reforming reaction. The gas mixture which has been heated in a heating unit passes through a distribution tube and is distributed evenly to the reforming units. The reforming room is composed of a reforming tube in which a reforming catalyst is charged, or two or more such reforming tubes, parallel to each other. After being reformed the high-temperature reformed gas is passed around the reforming tubes, and fed back to a manifold.

This application is a divisional of U.S. patent application Ser. No.10/777,187, filed Feb. 13, 2004, which is a divisional of U.S. patentapplication Ser. No. 09/940,628, filed Aug. 29, 2001 (Now U.S. Pat. No.6,833,126), and claims priority from Japanese Patent Application Nos.099269/2001, filed Mar. 30, 2001, and 133213/2001, filed Apr. 27, 2001,the entire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a method and apparatus for reforming ahydrocarbon-based fuel, alcohol, etc. into a fuel gas containinghydrogen, for industries which use high-purity hydrogen as a fuel, suchas for fuel cells.

2. Prior Art

When electric power is generated using fuel cells, hydrogen is suppliedto the fuel cells; a fuel gas containing hydrogen is produced from a rawmaterial consisting of hydrocarbon based fuels, e.g. butane or propane,or alcohol based fuel such as methanol; the raw material is reformed ina reforming vessel containing a catalyst, in which a mixture of the fuelgas, steam and air is reformed.

The reforming reaction proceeds at a rather high-temperature and heat isabsorbed during the reaction, so when a conventional reforming device isused, the mixed gas is heated sufficiently in a preheater, and using theheat retained in the gas, the temperature of the catalyst is increased,or is otherwise heated by an external means, so as to expedite thereforming reaction.

Recently, a self-heating system is currently used for a reformingdevice. In the self-heating system, a mixed gas and reforming catalystare heated by the oxidation of a part of the mixed gas and the gas isreformed by the heat.

If a gas mixture is supplied to one end of a reforming device filledwith a partial oxidation catalyst and a reforming catalyst, and if thereformed gas is discharged from the other end after the gas mixture hasmade contact with the partial oxidation catalyst and the reformingcatalyst, then only the upstream portion of the reforming catalyst nearthe partial oxidation catalyst is over-heated, and the temperature ofthe downstream portion of the reforming catalyst, located further awayfrom the partial oxidation catalyst increases after a time delay. As aresult, the temperature distribution of the reforming catalyst isuneven, therefore, a fairly long time is required before the temperatureof the entire reforming catalyst has been increased, so the reformingdevice cannot be started up quickly.

In addition, because part of the reforming catalyst is over-heated dueto the uneven temperatures distribution, deterioration of the catalyst,such as sintering occurs.

Recently, a new reforming device has been developed and is in practicaluse; the partial oxidation catalyst and the reforming catalyst areinstalled in multiple layers, so as to distribute the temperatureincrease of the reforming catalyst more evenly. This type of reformingdevice is typically classified into the series type shown in FIG. 1, andthe parallel type in FIG. 2.

In the series-type reforming device, the reforming room is arranged inmultiple stages (3 stages in FIG. 1) and each stage has a partialoxidation catalyst on the upstream side and a reforming catalystdownstream, and a gas mixture containing a fuel vapor such as methanol,steam and a small amount of air is introduced at one end of the device,and the reformed gas is discharged from the other end. To expedite thepartial oxidation reaction of the gas mixture, additional air is fedinto the second and third reforming rooms. In the series-type reformingdevice, the temperatures of the reforming catalysts in each stage areincreased automatically by the heat of the partial oxidation reaction,and the length of the passage in which the gas mixture contacts thereforming catalyst can be made long, so the advantage of a highreforming rate can be expected.

Conversely in the parallel-type reforming device, partial oxidationcatalysts and reforming catalysts are arranged in a number of stages (3stages in FIG. 2), in the same way as with the series-type device, andeach stage is separated from the others, and a gas mixture containing afuel vapor such as methanol, steam and a small amount of air is suppliedto each stage, and a reformed gas is discharged from each stage. Alsowith this parallel-type device, the temperatures of the reformingcatalysts in each stage can be increased evenly using internallygenerated heat, and because only the gas mixture is distributed to eachstage of the reforming device, the construction can be simplified whichis an advantage. If part of the reforming catalyst etc. deterioratesaccidentally, each stage can be quite easily replaced individually,which is also an advantage.

However, the aforementioned series- and parallel-type reforming devicesare accompanied with the following problems.

(1) With the series-type reforming device, air must be supplied to thereforming rooms at the second and subsequent stages from an externalsource, so the air piping is complicated and requires a dedicated space.The air supplied from outside must be mixed completely with the gasmixture in the small space between adjacent reforming rooms and then fedto the reforming rooms, but this space is normally small, so the mixingoften becomes incomplete. As a consequence, inappropriate reactions maysometimes take place, for example, irregularities may occur in thepartial oxidation or reforming reactions.(2) With the parallel-type reforming device, on the contrary, since thefuel mixture such as methanol, steam and air is mixed completelybeforehand and then fed to each reforming room, the problems mentionedabove for the series-type reforming device do not occur. However, as thelength of the passage in which the gas mixture contacts the reformingcatalyst is short, the necessary reforming rate may not be obtained whenthe distribution of reforming catalysts or the distribution of carriermaterials are not maintained evenly.

When a reforming device is used for fuel cells in an electric automobileetc., the motor must be started quickly by generating electric power bysupplying high-purity hydrogen into the stack of fuel cells as quicklyas possible. The device must also be as compact as possible.

However, with a conventional self-heating system of series- orparallel-type reforming devices, compactness of the device isinconsistent with a high reforming rate as described above.

The hydrogen, required to generate electric power in a fuel cell, isproduced by a reforming reaction using a raw material consisting ofeither a hydrocarbon based fuel, such as butane and propane, or analcohol based fuel, such as methanol. However, because the hydrogen-richreformed gas produced by the reforming reaction contains a large amountof carbon monoxide (CO) as an impurity, it should be removed beforesupplying it to a fuel cell that requires high-purity hydrogen. This isbecause if CO is fed into the fuel electrode of the fuel cell, it isadsorbed by the catalyst in the electrode, poisons the catalyst,decrease the reaction at the electrode, and lowers theelectricity-generating performance.

Under these circumstances, the reforming device is normally providedwith a CO removal unit filled with a CO removing catalyst, where aselective CO oxidation reaction (CO+½O₂→CO₂) or, if required, a COshifting reaction (CO+H₂O→CO₂+H₂) occurs, thus the concentration ofcarbon monoxide is reduced, in this additional mechanism.

With a reforming device that produces hydrogen-rich reformed gas from ahydrocarbon-based fuel or an alcohol fuel, the reforming reactionproceeds endothermically, so heat must be supplied to the reformingunit. In addition, it is also important to supply heat to increase therate of the reforming reaction. Therefore, in many cases, fuel gas,water and air are heated by an external heat source to a temperatureappropriate for the reforming reaction, to produce a high-temperaturevapor which is then fed to the reforming unit, or the gas mixture isheated up to such a temperature in the reforming unit where thereforming reaction takes place.

On the other hand, a CO removal unit containing a catalyst mainlyintended to decrease the concentration of CO contained in the reformedgas produced in the reforming unit. the selective CO oxidation reactionbegins at about 100 to 200° C. and a CO shift reaction occurs at about200 to 300° C. In addition these reactions are exothermic, thetemperature of the CO removal catalyst should be prevented fromincreasing in order to obtain a high CO removal rate. For this reason aconventional reforming device of the reforming unit must be designed tobe separate from the CO removal unit, or if an integrated design isused, a thermal insulation material is required to prevent the heattransfer from the reforming unit to the CO removing unit, and a methodof cooling the CO removal unit should be used.

Furthermore, carbon monoxide created in the reforming reaction poisonsthe electrode catalyst in the fuel cell as described above, andinterferes with the reaction of the electrode, so it should be removedfrom the reformed gas by a CO removal reaction. However, since the COremoval reaction is exothermic, if heat is transmitted from thereforming unit to the carbon monoxide removal portion (CO removal unit),the CO removal reaction does not proceed.

Consequently, in an integrated reforming device composed of a reformingunit and a CO removal unit, the heat transfer from the reforming unit tothe CO removal unit must be decreased and the loss of heat from thereforming unit at high operating temperatures must be prevented.

Conventionally, the reforming catalyst is installed in a singlecylindrical or square vessel, therefore when the device generates alarge output, the sectional area of the passages in the catalyst vesselis also large, often resulting in an irregular distribution of fuel gasflow in the catalyst vessel, and a satisfactory reforming reaction isoften not achieved.

When the reforming unit is constructed with the reforming catalystinstalled in a single catalyst vessel, if even part of the catalystdeteriorates as a result of operating with an unbalanced flow of the gasmixture, the whole reforming unit must be replaced.

SUMMARY OF THE INVENTION

The present invention aims at solving the aforementioned variousproblems. The first object of the present invention is to offer areforming method and a reforming apparatus, in which the temperature ofthe reforming catalyst can be increased, evenly and rapidly at the timeof starting, a reformed gas with a high degree of reforming can beproduced, and the apparatus is compact and can be easily maintained.

The second object of the present invention is to provide a smallreforming apparatus that can produce high-purity hydrogen gas by (1)increasing the temperature of the reforming catalyst, while preventingheat losses caused by heat transfer from the reforming catalyst to theoutside, (2) adjusting the cross section of the reforming tubes to givean appropriate area taking into account the number of reforming tubesand the output, thereby making the gas mixture flow evenly through thereforming catalyst, and more preferably (3) by improving the CO removalreaction by suppressing the heat transfer from the reforming unit to theCO removal unit.

To achieve the first object of the present invention, two or morereforming rooms (6) are connected in series; a gas mixture (2) of fuel,water and air is supplied to one end of each unit, and a reformed gascontaining hydrogen is discharged from the other end; a first catalyst(8 a) that catalyzes the partial oxidation of the fuel in an oxygenenvironment is installed on the upstream side of each of theaforementioned reforming rooms; a second catalyst (8 b) that catalyzesthe reforming reaction is installed on the downstream side thereof; theabove-mentioned gas mixture is supplied directly to one end of eachreforming room, and the reformed gas is discharged from the end of thereforming room furthest downstream.

According to the aforementioned reforming method of the presentinvention, the second catalyst in each reforming room can be evenly andquickly heated up by the internal heating produced by theabove-mentioned self-heating effect in each reforming room, therebyreformed gas containing high-purity hydrogen gas can be producedimmediately after starting up. In addition, because the length of thepassage in which the gas mixture contacts the second catalyst can bemade long, the degree of reforming can also be improved.

An identical catalyst that can accelerate both the partial oxidationreaction and the reforming reaction may also be used for theaforementioned first catalyst (8 a) and second catalyst (8 b).

In a self-heating system currently used in a reforming device, differentcatalysts are normally used to accelerate the oxidation reaction and thereforming reaction and these are installed on the upstream anddownstream sides respectively. However, some catalysts can expedite boththe partial oxidation and reforming reactions. When such a catalyst isincorporated, the reforming room is completely filled with the catalystand the temperature of the catalyst is increased by the self-heatingeffect, thus the reforming reaction can be initiated very quickly fromthe start of operation.

The present invention also offers a reforming method using a reformingtube (10) comprised of two or more of the above-mentioned reformingrooms (6) connected in series and a reformer housing (12) that housesthe aforementioned reforming tube, wherein a high-temperature heatinggas (16) is introduced into the space (14) formed between the reformingtube and the reformer housing, and after the above-mentioned firstcatalyst (8 a) and the second catalyst (8 b) have been heated up fromoutside the reforming room, the gas mixture (2) is supplied into eachreforming room and reformed.

The present invention also offers a reforming method with the novelcharacteristics that a high-temperature heating gas (16) is supplieddirectly to one end of each of the aforementioned reforming rooms (6),and is discharged from the other end of the most downstream reformingroom, and after the above-mentioned first catalyst (8 a) and secondcatalyst (8 b) are heated up from the inside of the reforming room, thegas mixture (2) is fed to each reforming room where it is reformed.

To efficiently reform a gas mixture in a reformer, it is considerednecessary to heat the reforming catalyst sufficiently, beforehand.According to the above-mentioned reforming method, the first and secondcatalysts are heated up evenly and satisfactorily in advance fromoutside and/or inside using a high-temperature heating gas that has beenheated using an external combustor etc., and then the supply of heatinggas is stopped, and the gas mixture is fed in, therefore, the reformingreaction can take place efficiently immediately after the gas mixture issupplied. In other words, the reforming reaction can be initiatedquickly after start-up, and in addition, the cost of the fuels is alsosaved.

The present invention also provides a reformer equipped with a mixed gasfeeding tube (18) that supplies the gas mixture (2) of fuel, water andair and a reforming tube (10) that converts the above-mentioned mixedgas to a reformed gas (4) containing hydrogen, in which theaforementioned reforming tube is comprised of two or more reformingrooms (6) in series, where the gas mixture (2) is fed in to one endthereof and the reformed gas (4) containing hydrogen is discharged fromthe other end thereof; each of the aforementioned reforming rooms isfilled with a first catalyst (8 a) for partial oxidation in anoxygen-rich environment on the upstream side and a second catalyst (8 b)for reforming downstream, and the above-mentioned mixed gas feed tube isprovided with a means of feeding gas (20) that supplies the gas mixturedirectly to each reforming room.

The reforming rooms are connected in series, and the gas mixture thathas been thoroughly premixed is supplied directly to each reformingroom, thereby the second catalyst can be heated up by the self-heatingeffect, at an early stage in each reforming room. In addition, becausethe gas mixture supplied to the upstream reforming room also passesthrough the downstream reforming rooms and is discharged from the otherend of the most downstream reforming room, the length of the passage inwhich the gas contacts the second catalysts is long, so the reformingrate can be improved. Compared to a conventional series-type reformingtube, no external piping needs to be introduced, therefore, theconstruction is simplified and the equipment can be made compact.

In addition, modular reforming tubes can be used, and the number ofreforming tubes can be increased or decreased depending on the outputrequired for the reformer. Also, since the gas mixture can bedistributed evenly to each unit, the gas mixture that flows through thecatalyst can be prevented from being unevenly distributed across thesectional area, so the reforming reaction can be accelerated. Inaddition, because the reforming tubes of each unit can be replaced, theapparatus can be easily maintained.

Here, the aforementioned means of feeding gas (20) is an outer cylinder(24) that covers at least part of the downstream end and side surface ofthe aforementioned reforming tube (10), and the circumferential gap (22)between the reforming tube and the cylinder forms a passage for themixed gas (2); on the side surface of the above-mentioned reformingtube, inlet ports (26) are provided to feed the gas mixture to eachreforming room from the above-mentioned gap; each of the aforementionedinlet ports is provided with flow control mechanisms (28 a, 28 b) orflow regulate means (32 a, 32 b) for adjusting the flow of the gasmixture supplied to each reforming room. This construction is also thepreferred method of supplying the gas mixture to each reforming room.

The outer cylinder is arranged so that it covers the side surface of thereforming tube, and the gap between the outer cylinder and the reformingtube is used as a flow passage for the gas mixture, thereby piping is nolonger needed to supply the gas mixture to each reforming room, so thereformer can be made simple and compact. This outer cylinder can alsosuppress heat transfer from the reforming room to outside.

The reason that the inlet ports disposed on the reforming tube areprovided with flow control mechanisms or flow regulate means is that ifsimple inlet ports are constructed on the reforming tube to supply thegas mixture, the gas mixture cannot be supplied to each reforming roomwith the appropriate distribution. More explicitly, because the suppliedgas mixture tends to flow into a passage with a low pressure drop,therefore if only inlet ports are provided, most of the gas mixture willflow into the most downstream reforming room. A variable mechanism etc.disposed at each inlet port provides an appropriate pressure drop(load), so that the gas mixture distributes in each reforming room in anoptimal manner.

The aforementioned means of feeding gas (20) are composed of apenetration tube (34) with the structure of a hollow tube that makes theabove-mentioned gas mixture (2) flow through the inside of at least onereforming room, from one downstream end of the aforementioned reformingtube (10); the above-mentioned penetration tube is provided with inletports (36 a, 36 b) that supply the gas mixture to each reforming room;and at the above-mentioned inlet ports, flow control mechanisms (28 a,28 b) or flow regulate means (32 a, 32 b) are provided to adjust theflow of the gas mixture introduced into each reforming room, using theaforementioned means, therefore the gas mixture can be fed appropriatelyto each reforming room.

The gas mixture can also be supplied to each reforming room from theinside of the reforming tube using a penetration tube in place of theabove-mentioned outer cylinder. In this case, flow control mechanisms orflow regulate means are also arranged at the inlet ports for the samereason as described above. Here, the flow control mechanisms and flowregulate means may be composed of flow control valves and orifices,respectively.

Other preferable configurations according to the present inventioninclude the provision of a reformer housing (12) that houses theaforementioned reforming tube (10) and an initial heating gas tube (38a) that introduces high-temperature heating gas (16) into the space (14)formed between the above-mentioned reformer housing and theaforementioned reforming tube; then or after the reforming room has beenheated up from the outside, a second heating gas tube (38 b), connectedto the aforementioned mixed gas feed tube (18) introduceshigh-temperature heating gas (16) from the outside, and after thereforming room has been heated up from the inside, the gas mixture issupplied.

The high-temperature heating gas, after being heated up in a combustoretc., is introduced into the space between the reformer housing and thereforming tube, and preferably it is directed towards the reformingtube, thereby the reforming tube and the catalyst are heated up from theoutside, or by supplying the heating gas to each reforming room throughthe mixed gas feed tube, the catalyst etc. can be heated upsatisfactorily from the inside, and then the introduction of the heatinggas is stopped, and the gas mixture is introduced. According to thismethod, the reforming reaction can be implemented quickly andefficiently from the beginning.

To achieve the aforementioned second object, the present inventionprovides a reforming apparatus that converts a mixed gas (102) comprisedof fuel gas, steam and air, into hydrogen; the above-mentioned reformingapparatus is composed of a heating unit (104) that vaporizes and heatsthe aforementioned gas mixture, a distribution tube (108) that evenlydistributes the heated gas mixture to a plurality of branch ports (106)at one end thereof, a reforming unit (114) filled with a reformingcatalyst (112) to catalyze a reforming reaction in the aforementionedgas mixture, a manifold (116) in which the above-mentioned distributiontube is disposed, a CO removal unit (124) fully filled with a COremoving catalyst (122) that catalyzes the CO removal reaction of thegas (118) reformed in the aforementioned reforming unit, and a casing(126) that houses the above-mentioned reforming unit, the aforementionedmanifold and the above-mentioned CO removal unit; the aforementionedreforming unit is configured with a reforming room (132) and a feedbackmechanism (134), in which the reforming room is composed of a reformingtube (130) one end of which is connected to the aforementioned branchport and reformed gas is discharged from the other end thereof, or twoor more such reforming tubes arranged in parallel, and the feedbackmechanism allows the above-mentioned reformed gas to flow through theouter periphery of the aforementioned reforming tube and sends the gasto the above-mentioned manifold.

The gas mixture (102), vaporized and heated in the heating unit (104),is distributed through the distribution tube (108) and is supplied toone reforming tube (130) or a plurality of tubes (130), and undergoes areforming reaction in the reforming tube or tubes. Here, an orifice or asintered panel or the like is provided at the inlet of the distributiontube, thus the gas mixture is distributed to the reforming tube ortubes; and the cross section of the reforming tube is adjusted accordingto the relationship between the number of reforming tubes and theoutput, to give an optimum area, that is, when a small amount of thereformed gas is demanded, the number of reforming tubes is reduced, anda reforming tube with a slightly smaller sectional area is used; when alarge amount of reformed gas is required, the number of reforming tubesis increased and also a reforming tube with a slightly larger crosssection is used, thereby the gas mixture is distributed evenly acrossthe cross section and along the length of each reforming tube, and inthis way, the gas mixture can be diffused uniformly into the interior ofeach reforming tube. As a result, the gas mixture and the reformingcatalyst can be made to contact each other efficiently, and thereforming reaction can be expedited.

In addition, by sending the high-temperature reformed gas to themanifold (116) through the outer periphery of the reforming tube, heatlosses from the reforming tube to the outside can be decreased.

Here, the aforementioned CO removal unit (124) can preferablycommunicate with the above-mentioned manifold (116), and be positionedopposite the aforementioned reforming unit (114).

According to the reforming apparatus of the present invention, becausethe reforming unit (114) wherein a reaction takes place at a rather hightemperature can be connected freely to the CO removal unit (124) inwhich another reaction occurs at a temperature lower than the abovetemperature, heat transmission from the reforming unit to the CO removalunit can be prevented by, for example, positioning the manifold betweenthem, so even if the reforming unit and the CO removal unit are formedas an integral unit, the reforming apparatus can be made smaller insize.

In the above, the aforementioned feedback mechanism (134) may alsopreferably send the above-mentioned reformed gas (118) to theaforementioned manifold, through the space between the aforementionedadjacent reforming tubes (130) or through a reformed gas passage (136)consisting of a longitudinal gap parallel to the axis of the reformingtube, formed between the above-mentioned reforming tube and theaforementioned casing (126).

The gap created between adjacent reforming tubes (130) or between theaforementioned reforming tube and the above-mentioned casing (126) canbe used as a passage (136) for the reformed gas, and by sending thehigh-temperature reformed gas (118) to the manifold (116) along theouter periphery of the reforming tube, the high-temperature reformed gascan completely fill the space around the outer periphery of thereforming tube, thus efficiently suppressing heat transfer from thereforming tube to the outside, and special piping etc. is no longerneeded to send the reformed gas to the manifold, therefore, theconstruction of the apparatus can be simplified.

In addition, the aforementioned reforming tube (130) can preferably beremovable and replaceable.

Because the reforming tube (130) filled with the reforming catalyst (12)is structured as a modular unit, each reforming tube can be inspectedand replaced, so the apparatus can be maintained more easily than in theprior art.

Moreover, a fuel trap unit (138) that removes fuel gas from the reformedgas (118) can be disposed between the aforementioned manifold (116) andthe above-mentioned CO removal unit (124).

The fuel trap unit (138) installed between the manifold (116) and the COremoval unit (124), can prevent fuel gas that was unreformed in thereforming unit after entering the CO removal unit, and adhering to theCO removal catalyst, resulting in interference with the CO selectiveoxidation reaction or the CO shift reaction, thus, CO can be removedefficiently, and at the same time heat produced in the reforming unit(114) can also be prevented from being transmitted to the CO removalunit and the reformed gas (118) can be cooled in the fuel trap unit.

It is also preferred that a feed tube (142) is provided that suppliesoxygen, air or steam to the reformed gas (118) as it is being sent fromthe aforementioned manifold (116) to the above-mentioned CO removal unit(124).

As oxygen (air) or steam is supplied to the reformed gas (118) as themixture is being sent into the CO removal unit, an appropriate amount ofoxygen and steam can be provided to satisfy the above-mentionedselective CO oxidation reaction (CO+0.5O₂→CO₂) or the CO shift reaction(CO+H₂O→CO₂+H₂), and at the same time, by cooling the reformed gas, thetemperature of the CO removal unit can be prevented from increasingexcessively, and so the CO removal reaction can proceed more rapidly.

Here, the aforementioned CO removal unit (124) is composed of onepartition or two or more partitions; on the upstream side of eachpartition, feed tubes (142 a, 142 b) can be constructed to supplyoxygen, air or steam.

For example, the CO removal unit can be divided into two partitions; asteam feed tube is installed in front of the upstream partition filledwith a catalyst appropriate for the CO shift reaction, and an oxygenfeed tube is provided before the downstream partition charged with acatalyst suitable for the selective CO oxidation reaction, thus CO canbe removed efficiently, and a reformed gas (refined gas) with a higherhydrogen purity than in the prior art can be produced.

Other objects and advantages of the present invention are revealed inthe following paragraphs referring to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a conventional series-type reformingdevice.

FIG. 2 is a schematic view of a conventional parallel-type reformingdevice.

FIG. 3 is a schematic view of the reforming method according to thepresent invention.

FIG. 4 shows a configuration of the first embodiment of the reformingapparatus according to the present invention.

FIG. 5 shows a configuration of the second embodiment of the reformingapparatus according to the present invention.

FIG. 6 shows a configuration of the third embodiment of the reformingapparatus according to the present invention.

FIG. 7 is a sectional view along the line X-X in FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENTS

The following paragraphs describe preferred embodiments of the presentinvention referring to the drawings. The same reference numbers are usedto describe identical portions, and no duplicate descriptions are given.

The present invention relates to the method and apparatus for convertinga gas mixture containing fuel gas, steam and air into a fuel gascontaining hydrogen, mainly intended for use on an automobile etc.Principally as a hydrogen feed source for a fuel cell. Since it isexpected that methanol can be supplied stably at a low cost in thefuture, the case of reforming methanol using methanol as the fuel isdescribed emphatically below.

Generally, a methanol reforming device causes methanol (CH₃OH) to reactwith steam (H₂O) using a catalyst; as a result of the reactions shown bythe following equations (A) and (B), methanol (CH₃OH) is reformed andhydrogen (H₂) is generated.

CH₃OH→CO+2H₂−21.7 Kcal  (A)

CH₃OH+H₂O→CO₂+3H₂−11.9 Kcal  (B)

CH₃OH+0.5O₂→CO₂+2H₂+45.3 Kcal  (C)

CO+0.5O₂→CO₂+67.6 Kcal  (D)

CO+H₂O→CO₂+H₂+9.8 Kcal  (E)

Obviously from equations (A) and (B), the methanol reforming reaction isendothermic, therefore, to increase the hydrogen-production rate andincrease the reaction rate, heat must be added, and heat dissipationfrom the reforming portion (reforming unit) must be prevented.

Therefore, in a conventional reforming device, a combustion chamber isinstalled adjacent to the reforming unit to heat up the unit, or thefuel gas etc. is preheated using a preheater and then fed into thereforming unit, or using the reaction (C), the reforming unit is heatedinternally (auto-heating) system. In these cases, heat insulationmaterial etc. is used to prevent heat from being lost from the reformingunit to the outside.

FIG. 3 shows a general concept of the reforming method according to thepresent invention, and FIG. 4 is a configuration view showing the firstembodiment of the reforming apparatus using the reformer according tothe present invention.

The reforming apparatus 1 in this embodiment is composed generally of anevaporator 39, a reformer 40, a CO removal unit 42 and a combustor 44.Here, the reformer 40 and the CO removal unit 42 are installed in arectangular casing 46, separately from each other. A communication port48 is provided in the partition between the reformer 40 and the COremoval unit 42, through which the reformed gas 4 is sent.

A hydrogen gas feed line 52 is connected to the CO removal unit 42 tosupply the hydrogen-rich reformed gas (refined gas 50) produced byremoving carbon monoxide from the reformed gas 4 created through areforming reaction in the reformer 40, to a fuel cell (not illustrated)disposed outside the main unit of the reforming apparatus.

The evaporator 39 is provided with a methanol feed tube 39 a thatsupplies methanol reforming fuel from an external device, and awater/air feed tube 39 b to supply water and air.

Methanol, water and air are mixed in the evaporator 39, heated up by aheat source using, for instance, combustion heat, to produce a gasmixture 2 with a temperature as high as about 180˜230° C. which is fedunder pressure to the mixed gas feed tube 18.

The mixed gas feed tube 18 passes into the reformer 40, and branchesinside. Along the length and at the end of each branch, are installedscrewed gas feed ports 54 and a plurality of reforming tubes 10 eachwith three reforming rooms connected in series which take in the gasmixture 2 at one end and discharge the reformed gas 4 containinghydrogen from the other end (starting from the bottom, each reformingroom is called “lower reforming room 6 a”, “middle reforming room 6 b”and “upper reforming room 6 c”).

Individual reforming tubes 10 can be freely removed from the gas feedport 54 by unscrewing, so each tube can be replaced independently fromthe others. The three reforming rooms 6 a, 6 b and 6 c are connectedtogether by screw threads provided on the outer surface of the openingat the bottom end of each reforming room, and screw threads machined onthe inner periphery of the opening at the top end. In this way, eachunit of a reforming tube or room can be replaced, so the apparatus canbe maintained more easily than in the prior art.

Inside each reforming room, a first catalyst that catalyzes the partialoxidation in an oxygen environment (called the “partial oxidationcatalyst 8 a”) is filled in the bottom, that is, upstream in thedirection of the flow of the mixed gas 2, while a second catalyst forreforming (called the “reforming catalyst 8 b”) is charged in thebottom, i.e. downstream in the direction of the gas flow. Therefore, thepartial oxidation reaction and the reforming reaction take place in theupstream and downstream portions of each reforming room, respectively.The partial oxidation and reforming catalysts can also be arranged to behoneycomb shaped catalysts.

Generally, different catalysts are used for each of the above catalysts;palladium for the partial oxidation catalyst 8 a and copper zinc alloyfor the reforming catalyst 8 b. However, by using a catalyst that canaccelerate both the partial oxidation and the reforming reactions, suchas heat-resistant copper-zinc alloys, both catalysts can be madeidentical to each other. As shown in FIG. 4, an outer cylinder 24 coversthe entire lower reforming room 6 a, the entire middle reforming room 6b and the lower end of the upper reforming room 6 c, that is, one end ofthe bottom portion of the reforming tube 10 and about two thirds of thelower portion of the side surface. The lower end of the outer cylinder24 is connected to the gas feed port 54, and the upper end thereof isattached to the side surface of the reforming tube 10. The portion ofthe reforming tube 10 enclosed by the outer cylinder 24 forms a coaxialdouble-walled tube in which the peripheral gap 22 provides a passage forthe gas mixture 2, leading to the reforming tube 10.

On the side surface of the reforming tube 10 where the lower end of themiddle reforming room 6 b and the lower end of the upper reforming room6 c are located and enclosed by the outer cylinder 24, there are inletports 26 a and 26 b that supply the gas mixture 2 to the middlereforming room 6 b and the upper reforming room 6 c, respectively, fromthe gap 22; these inlet ports 26 a, 26 b are provided with flow controlmechanisms 28 a, 28 b composed of flow control valves that can adjustthe diameters of the inlet ports. The flow control mechanisms 28 a, 28 badjust the flows of the gas mixture 2 supplied to the middle and upperreforming rooms 6 b and 6 c. The gas mixture 2 is supplied to the lowerreforming room 6 a through an opening at the bottom of the lowerreforming room 6 a.

In addition, a sintered panel 56 is provided in the opening at the lowerend of each reforming room. Here, because the sintered panel 56 is astructure with many fine holes, the gas mixture 2 passes through thesefine holes and flows evenly into the reforming room.

Next, features of the reforming apparatus of this embodiment aredescribed by following the flow of the supply of the gas mixture 2.

Part of the gas mixture 2, sent under pressure towards the gas feed port54 through the mixed gas feed tube 18, is supplied as shown by the arrowα in FIG. 4, from lower end of the reforming tube 10 to the lowerreforming room 6 a, and the rest is supplied to the middle and upperreforming rooms 6 b and 6 c through the gap 22 and inlet ports 26 a, 26b as shown by the arrow β.

Part of the gas mixture 2 sent to each reforming room contacts thepartial oxidation catalyst 8 a loaded into the upstream end, generatesheat due to the partial oxidation reaction (CH₃OH+0.5O₂→CO₂+2H₂+45.3Kcal), and directly heats the balance of the gas mixture and theadjacent reforming catalyst 8 b on the downstream side, to temperaturesappropriate for the reforming reaction (auto-heating system). As therest of the gas mixture 2 is heated up, it stimulates the reformingreaction by contacting the active surface of the reforming catalyst 8 bon the downstream side, so producing the reformed gas 4.

The reforming reaction (CH₃OH→CO+2H₂−21.7 Kcal, CH₃OH+H₂O→CO₂+3H₂−11.9Kcal) is an endothermic reaction, therefore, the heat of thisendothermic reaction is added by the reaction heat due to the partialoxidation reaction.

The gas mixture 2, having entered the lower reforming room 6 a as shownby the arrow α in FIG. 4, is subjected to the partial oxidation andreforming reactions, and then moves to the middle reforming room 6 b. Atthis time, the reacted gas mixture is mixed with the gas mixture 2 (β)supplied through the inlet ports 26 a located at the bottom end of themiddle reforming room 6 b, in the small space 58 formed between thelower reforming room 6 a and the middle reforming room 6 b.

In the middle reforming room 6 b, similar partial oxidation andreforming reactions also take place, and after these reactions, the gasmixture moves to the upper reforming room 6 c. Also at this time, thegas mixture 2 is fed in through the inlet port 28 b in the same way asabove, and mixing of the gases takes place in the small space 58 formedbetween the middle and upper reforming rooms 6 b and 6 c.

Identical partial oxidation and reforming reactions occur also in theupper reforming room 6 c, as described above, and after that,hydrogen-rich reformed gas 4 is discharged from an opening at the topend of the upper reforming room 6 c.

That is, the gas mixture 2 (α) supplied to the bottom end of the lowerreforming room 6 a is reformed in the three (lower, middle and upper)reforming rooms, while the gas mixture 2 (β) supplied through the inletports 26 a is reformed in two (middle and upper) reforming rooms, andthe gas mixture 2 supplied through the inlet ports 26 b is reformed inone (upper) reforming room. Therefore, the total length over which thegas mixture 2 is in contact with the reforming catalyzer 8 b isincreased, so the reforming rate is improved and is higher than that ofa conventional parallel-type reformer.

Since internal heating is provided by the auto-heating system at anumber of stages in each reforming room, the temperature of thereforming catalyst 8 b can be increased evenly and rather quickly afterthe reforming apparatus is started up without causing irregularities inthe temperature distribution.

In addition, because methanol vapor, steam and air are premixedcompletely in the evaporator 39 to produce the gas mixture 2 which issupplied to each reforming room, unlike the series-type reformer, theproblem of incomplete mixing of the gas mixture and air never occurs.Moreover, no piping etc. is required to introduce air from the outside,instead the gas mixture 2 is distributed internally to each reformingroom and therefore, the construction of the reformer 40 can besimplified.

At inlet ports 26 a, 26 b, flow control mechanisms 28 a, 28 b composedof flow control valves are provided to adjust the flows of the gasmixture 2 entering the reforming rooms 6 b, 6 c, and these flow controlvalves are equipped with constrictions (not illustrated) that are openedand closed by external power. By adjusting these constrictions, the flowof the gas mixture 2 supplied to each reforming room can be adjusted. Inplace of the flow control mechanisms 28 a, 28 b, flow regulate means 32a, 32 b such as orifices can also be used.

The reforming apparatus 1 of this embodiment of the present invention isalso provided with an initial heating gas tube 38 a that introduceshigh-temperature heating gas 16 from outside into the space 14 betweenthe reformer housing 12 and the reforming tube 10 and directs the gastowards the reforming tube 10.

In a conventional reformer, the reforming tube is warmed up directly bythe heat produced from the partial oxidation catalyst 8 a and thereforming catalyst 8 b. Consequently, a fairly long time is requiredbefore the reforming catalyst is heated sufficiently and the reformer isready for operation, therefore, the reformer cannot satisfy the need forstarting the device quickly and supplying hydrogen gas soon.

In the reforming apparatus 1 of this embodiment of the presentinvention, the reforming tube 10, the reforming catalyst 8 b, etc. canbe heated up from outside while the dissipation of heat from thereforming catalyzer etc. to the outside can be prevented, as gases suchas air are heated by the combustor 44 to produce the high-temperatureheating gas 16 which is introduced into the reformer 40 through thefirst heating gas tube 38 a and injected into the space 14 between thereformer housing 12 and the reforming tube 10.

More explicitly, because the reforming tube 10 and the reformingcatalyst 8 b are previously warmed up (preheated), reformed gas 4 with ahigh reforming rate can be produced soon after the reformer 40 isstarted up. The gas mixture 2 is supplied to each reforming room afterwarming up is finished and the introduction and ejection of the heatinggas 16 is stopped. Instead of using the heating gas 16, it is alsopossible to preheat the reforming tube 10, the reforming catalyst 8 b,etc. by installing a heating wire etc. around or inside the reformingtube 10.

The gas mixture with a large concentration of hydrogen produced by thereforming reaction in the reforming tube 10 is discharged from the topof the reforming tube 10, completely fills the space 14 inside thereformer housing 12, and then passes through the communication port 48to the CO removal unit 42 installed adjacent to the reformer 40.

In the CO removal unit 42, excess carbon monoxide (CO) contained in thereformed gas mixture (reformed gas 4) is removed. This is because ifcarbon monoxide is supplied to the fuel electrode of a fuel cell, it isadsorbed on the active parts of the catalyst on the fuel electrode incompetition with hydrogen, thereby the electrode catalyst in the fuelcell is poisoned, interfering with the reaction on the electrode anddegrading the power generating performance, so it has to be prevented.

The CO removal unit 42 is filled with a CO removal catalyst 60, whichpromotes the CO shift reaction (CO+H₂O→CO₂+H₂) and the selective COoxidation reaction (CO+0.5O₂→CO₂) in the reformed gas 4 sent from thereformer 40, and the carbon monoxide poison is removed.

The reformed gas 4, after the carbon monoxide has been satisfactorilyremoved in the CO removal unit 42, is now a refined gas which flows outof the refined gas outlet port 62 provided at the furthest downstreamportion of the CO removal unit 42, and is supplied to the hydrogenelectrode (anode: not illustrated) of the fuel cell through a hydrogengas feed line 52, where it is used to generate electric power.

FIG. 5 shows a second embodiment of the reforming apparatus according tothe present invention. The component parts of the reforming apparatus 3of this embodiment, other than the penetration tube (gas feed means) andthe second heating gas tube to be described in detail later areidentical to those of the reforming apparatus 1 of the first embodiment,therefore, these portions are not described below.

The mixed gas feed tube 18 is joined with a screwed connection to thereforming tube 10 comprised of a three-stage reforming room with lower,middle and upper stages (6 a, 6 b, 6 c), as in the first embodiment. Themixed gas feed tube 18 is connected to a penetration tube 34 composed ofa hollow tube that penetrates the interior of the lower reforming room 6a and the middle reforming room 6 b from the end of the reforming tube10 on the upstream side, and the penetration tube 34 allows the gasmixture 2 to flow into the interior thereof.

Inlet ports 36 a, 36 b are provided in the surface of the penetrationtube 34 near the bottom ends of the middle and upper reforming rooms 6b, 6 c to supply the gas mixture 2 to the rooms 6 b and 6 c,respectively. These inlet ports are equipped with flow controlmechanisms 28 a, 28 b composed of flow control valves that adjust theflows of the gas mixture 2 supplied to each reforming room. It is ofcourse possible, as in the first embodiment of the reforming apparatusaccording to the present invention, that flow regulate means 32 a, 32 bsuch as orifices are used in place of the flow control mechanisms 28 a,28 b.

Part of the gas mixture 2, supplied through the mixed gas feed tube 18,passes from the bottom of the reforming tube 10, to the lower reformingroom 6 a as shown by the arrow α′ in FIG. 5, and the rest of the gasmixture (β′) flows into the penetration tube 34. The gas mixture 2supplied to the lower reforming room 6 a undergoes partial oxidation andreforming reactions as described before, and then flows into the middlereforming room 6 b. At this time, the gas mixture (α′) mixes with thegas mixture 2 (β′) entering through the inlet port 36 a, in the smallspace 58 formed between the lower and middle reforming rooms 6 a, 6 b.Partial oxidation and reforming reactions also take place in the middlereforming room 6 b in the same way, and after reacting the gas mixtureflows into the upper reforming room 6 c. In this case too, the gasmixture 2 (β′) is supplied through the inlet port 36 b, and mixes in thesmall space formed between the middle and upper reforming rooms 6 b and6 c. The gas mixture 2, after also being partially oxidized and reformedin the upper reforming room 6 c as described above, is discharged fromthe opening at the top of the upper reforming room 6 c as a reformed gas4 rich in hydrogen.

In other words, in the reforming apparatus 3 of this embodiment, thereforming catalyst 8 b can also be heated up evenly without anyirregularity in the temperature distribution, in each reforming room,and the length of the passage in which the gas mixture 2 is in contactwith the reforming catalyst 8 b can be made longer than in the priorart, therefore, the reforming rate can be increased. In addition, thegas mixture 2 can be premixed before being fed to each reforming room.Furthermore, because nothing is attached to the outer periphery of thereforming tube 10, cylindrical reforming tubes 10, if used, can bearranged conveniently inside the reformer housing 12.

As shown in the reforming tube illustrated on the right side of FIG. 5(the equipment is omitted from illustration on the left side), wheneverrequired, an air inlet tube 64 can be incorporated for introducingoutside air into the inside of the penetration tube 34, and after thegas mixture (β′) is completely mixed with air introduced through the airinlet tube 64 inside the penetration tube 34, the gas mixture can besupplied to the middle and upper reforming rooms 6 b, 6 c. By mixing airwith the gas mixture 2 (β′), the oxygen concentration thereof can beadjusted, and the partial oxidation reactions in the middle and upperreforming rooms 6 b, 6 c can be accelerated or controlled.

In the reforming apparatus 3 of this embodiment, in addition to thefirst heating gas tube 38 a used in the first embodiment, a secondheating gas tube 38 b is connected to the mixed gas feed tube 18 so thathigh-temperature gas 16 can be introduced from the combustor 44. Partnumber 66 represents a gate valve.

High-temperature gas 16 is introduced through the first high-temperaturegas tube 38 a into the space 14 inside the reformer housing 12, and thereforming tube 10 and the reforming catalyst 8 b are heated fromoutside, and also the high-temperature gas 16 is introduced into thereforming tube 10 through the mixed gas feed tube 18, thus heating thereforming tube 10 and the reforming catalyst 8 b internally. After thereforming catalyst 8 b is completely preheated, the flow ofhigh-temperature gas 16 is stopped, the gas mixture 2 is fed to eachreforming room, thereby reformed gas 4 with a high degree of reformingcan be obtained immediately after supplying the gas mixture 2. Inaddition, such a preheating process is also preferable because itprevents fuel or water from being condensed in the reforming catalyst 8b.

FIG. 6 shows a general view of the third embodiment of the reformingapparatus according to the present invention, and FIG. 7 is a crosssectional view along the line X-X in FIG. 6.

In FIG. 6, the reforming apparatus 110 according to the presentinvention is separated generally into a heating unit 104, a reformingunit 114, a manifold 116, a CO removal unit 124 and a casing 126. Themain unit of the reforming apparatus 110 a is configured with thereforming unit 114, manifold 116 and CO removal unit 124 as anintegrated unit housed in a rectangular casing 126.

A fuel tube (not illustrated) is connected to the heating unit 104 tosupply fuel for combustion, and the fuel is burned and the combustionheat thereof is utilized as a heat source to evaporate and heat up thegas mixture in the same way as known in the prior art, therefore, adetailed description of the heating unit 104 is omitted.

In the heating unit 104 methanol, water and air are mixed, evaporatedand heated to about 200° C. to produce the gas mixture 102 which is sentto the distribution tube 108 in the main unit of the reforming apparatus110 a. The distribution tube 108 branches in the manifold 116 of themain unit of the reforming apparatus 110 a; each branch passage isprovided with an orifice (not illustrated), so that an equal amount ofthe gas mixture 102 is distributed to each branch. The end of eachbranch of the distribution tube 108 is equipped with a branch port 106which communicates with the reforming room 132.

The reforming room 132 is composed of nine cylindrical reforming tubes130 arranged parallel to each other in three rows of three tubes each.One end of each reforming tube 130 is connected to a branch port 106 ofthe distribution tube 108, and the other end thereof opens into thecasing 126. The individual reforming tubes 130 can be removed andreplaced.

In addition, a partial oxidation catalyst 128 is loaded into theinterior of each reforming tube at the upstream end for theaforementioned (C) reaction and a reforming catalyst 112 is loaded intomiddle and downstream portions thereof for the reforming reaction.

A passage 136 for the reformed gas is provided by the gaps in the axialdirection of the reforming tubes between the adjacent reforming tubes130 and between the reforming tubes and the casing 126, and this passagefor the reformed gas communicates with the manifold 116.

The high-temperature gas mixture 102 sent from the heating unit 104through the distribution tube 108 is distributed evenly as shown by thearrows a, and flows through each branch port 106 provided at the end ofeach branch tube 108. Each branch port 106 is joined to a reforming tube130 with a leak tight joint, and the gas mixture 102 enters eachreforming tube 130 from its branch port 106, and flows through thereforming tube 130. The gas mixture 102 is heated up to a temperatureappropriate for the reforming reaction after being partially oxidized inthe upstream portion of the reforming tube 130, and also heats thereforming catalyst 112, which catalyzes the reforming reaction as thegas contacts the reforming catalyst in the middle and downstreamportions, thus a hydrogen-rich reformed gas is produced (auto-heatingsystem).

Here, as the high-temperature gas mixture 102 is evenly distributed andsent into each reforming tube 130 and uniformly distributed across thecross section of the tube, irregularities in the flow of the gas mixturein the reforming catalyst are prevented and the reforming reaction cantake place more efficiently than in the case where the gas mixture ispassed through the same amount of the reforming catalyst contained in asingle catalyst vessel.

The reformed gas 118, having passed through the reforming tubes 130 andbeen subjected to a reforming reaction, is discharged from the ends ofthe reforming tubes, and changes its direction of flow through 1800 asshown by the arrows b in FIG. 7, flows into the reformed gas passages136, and enters the manifold 116 which communicates with the reformedgas passages 136.

The gas mixture that flows through the reforming catalyst undergoes anendothermic reforming reaction, and the temperature thereof decreases toa predetermined level, before it is discharged from the end of thereforming tube as a reformed gas; however, the temperature thereof isstill high, so the reformed gas 118 is made to flow through thereforming gas passages 136 where it contacts the outer periphery of thereforming tubes 130, so preventing heat from the reforming catalyst 112from being transmitted to the outside.

The manifold 116 collects the reformed gases flowing through eachreformed gas passage, and as shown in FIG. 6, extends across the wholeof the casing 126 in the direction perpendicular to the surface of thepaper and separates the reforming room 132 from the CO removal unit 124to be described later, therefore, the manifold also prevents heat fromthe reforming unit from being lost to the CO removal unit 124.

A fuel trap unit 138 is located between the manifold 116 and the COremoval unit 124, to remove any fuel gas that was not reformed in thereforming unit 114, therefore, fuel gas in the reformed gas 118, whichwas unreacted and collected in the manifold 116, is captured in thisfuel trap unit. This fuel trap unit which is adjacent to the manifold116 is provided with a communication port that communicates with themanifold at the bottom end thereof, and extends across the whole casingin the direction perpendicular to the surface of the paper, as shown inFIG. 6, in the same way as the manifold. The unreacted fuel gas isremoved from the reformed gas when the reformed gas flows through thefuel trap unit 138 from bottom to top. The removed fuel gas isdischarged to the outside through an exhaust pipe (not illustrated), andis discarded or reused as a fuel etc. to be burned in the heating unit.In the above, the fuel trap unit 138 also plays a role in separating thereforming room 132 from the CO removal unit 124.

The reformed gas 118 after leaving the fuel trap unit 138 flows from thetop of the fuel trap unit into a narrow space 148 formed adjacent to thefuel trap unit 138. A feed tube 142 a for supplying air or oxygen fromoutside is provided in the narrow space 148, wherein the reformed gas118 discharged from the fuel trap unit 138 is mixed with air or oxygensupplied from the feed tube 142 a. In this way, the temperature of thereformed gas 118 is decreased together with providing a supply of oxygennecessary for the selective CO oxidation reaction to be described later.

The narrow space 148 communicates at the bottom thereof with the COremoval unit 124, whereby the reformed gas 118 mixed with air etc.enters the CO removal unit. The CO removal unit 124 is divided into twoparts composed of the front and rear portions shown in FIG. 6; an air oroxygen feed tube 142 b is introduced from outside, between the front andrear portions. Because the CO removal unit is divided, air or oxygen canbe supplied at the inlet of each section, the CO removal reactions takeplace in multiple stages, the temperature rise produced by the COremoval reaction can be reduced near the upstream end of the CO removalcatalyst which acts dominantly, and an excessive temperature increase inparts of the CO removal catalyst is prevented, so that CO can be removedefficiently during the exothermic reaction.

An optimum catalyst for a selective CO oxidation reaction (for example,Ru) is loaded into the front and rear portions.

In addition, cooling tubes 152 a, 152 b are provided in the upstreamparts of the front and rear portions, to cool the catalyst bycirculating, for instance, cold water or air, using an external device.This is because the selective CO oxidation reaction generates a largeamount of heat (CO+0.5O₂→CO₂+67.6 Kcal), and by cooling the upstreamportion of the CO removal catalyst where the reaction mainly takesplace, the reaction can be driven towards the right.

In the CO removal unit 124, the selective CO oxidation reaction takesplace, and the carbon monoxide is removed completely from the reformedgas 118 to produce the refined gas 154 which flows out of the refinedgas outlet port 156 provided at the bottom of the rear stage, and issupplied to the hydrogen electrode (anode: not illustrated) of a fuelcell.

According to the aforementioned reforming method and reformer of thepresent invention, the gas mixture is supplied to reforming roomsconnected together in a number of stages, and each reforming room isheated by the auto-heating system, thereby the catalyst is heated upevenly so that it can reform the gas soon after the reformer is startedand the length of the passage in which the gas mixture undergoes thereforming reaction can be made long, so that the reformed gas with ahigh degree of reforming can be produced soon after operations begin.

In addition, by using detachable and replaceable reforming tubes androoms and by simplifying the means of supplying the gas mixture to eachreforming room, an easy to maintain, compact reformer is offered.

More preferably, by introducing high-temperature heating gas into theinterior of the reformer, the reforming tubes, catalysts, etc. can beheated from outside and/or internally, and by warming up (preheating)the reformer in advance, the reforming reaction can take placeefficiently and quickly soon after the operation begins so that reformedgas (refined gas) with a high degree of reforming can be fed to the fuelcell where electric power is generated.

The above-mentioned reforming apparatus according to the presentinvention can perform a complete reforming reaction by passing the gasmixture evenly into a reforming tube with an appropriate cross section,or into a plurality of such reforming tubes, thereby eliminatingirregularities in the flow of gas in the reforming catalyst, and causingthe gas mixture to contact the reforming catalyst efficiently. Inaddition, by making the high-temperature reformed gas flow around thereforming tubes, heat losses from the reforming catalyst to the outsideare reduced, and by preventing heat losses, the endothermic reformingreaction can be increased.

More preferably, a manifold etc. is inserted between the reforming unitand the CO removal unit, so as to prevent heat from being transmittedfrom the reforming unit to the CO removal unit, thus the exothermic COremoval reaction can be increased, so the concentration of carbonmonoxide contained in the refined gas can be reduced sufficiently, andin addition, the reforming apparatus can be reduced in size.

However, the present invention is not limited only to theabove-mentioned embodiments, but also covers various modifications aslong as the scope of the claims of the invention is not exceeded.

1-9. (canceled)
 10. In the reforming apparatus that converts a gasmixture comprising a fuel gas, steam and air, into hydrogen, a reformingapparatus comprising a heating unit for evaporating and heating the gasmixture, a distribution tube that distributes the heated gas mixtureevenly to a plurality of branch ports disposed at one end thereof, areforming unit filled with a reforming catalyst for catalyzing the gasmixture, a manifold comprising the distribution tube on the insidethereof, a CO removal unit filled with a CO removal catalyst used toremove CO from the gas reformed in the reforming unit, and a casing forhousing the reforming unit, the manifold and the CO removal unit,wherein the reforming unit comprises a reforming room composed of areforming tube of which one end is connected to the branch port and fromthe other end of which the reformed gas is discharged, or configured bydisposing two or more of the reforming tubes parallel to each other, anda feedback mechanism for passing the reformed gas around the outerperiphery of the reforming tubes and sending the gas to the manifold.11. The reforming apparatus specified in claim 10, wherein the COremoval unit is located opposite or parallel to the reforming unit andcommunicates with the manifold.
 12. The reforming apparatus specified inclaim 10, wherein the feedback mechanism sends the reformed gas to themanifold through a reformed gas passage formed by the space between thereforming tubes located close to each other or between the reformingtubes and the casing, in the axial direction of the reforming tubes. 13.The reforming apparatus specified in claim 10, wherein the reformingtubes can be freely removed and replaced.
 14. The reforming apparatusspecified in claim 10, wherein a fuel trap unit is disposed between themanifold and the CO removal unit, to remove fuel gas from the reformedgas.
 15. The reforming apparatus specified in claim 10, wherein themanifold comprises a feed tube or feeding oxygen, air or steam to thereformed gas sent to the CO removal unit.
 16. The reforming apparatusspecified in claim 15, wherein the CO removal unit comprises one sectionor two or more sections, and feed tubes are disposed on the upstreamside of each section to supply oxygen, air or steam.